Tumor-specific cytolytic CD4 T cells mediate immunity against human cancer

Establishment of a novel NFAT-GFP reporter platform useful for the functional avidity maturation of HLA class II-restricted TCRs

CD4+ T cells that recognize antigenic peptides presented on HLA class II are essential for inducing an optimal anti-tumor immune response, and adoptive transfer of tumor antigen-specific TCR-transduced CD4+ T cells with high responsiveness against tumor is a promising strategy for cancer treatment. Whereas a precise evaluation method of functional avidity, an indicator of T cell responsiveness against tumors, has been established for HLA class I-restricted TCRs, it remains unestablished for HLA class II-restricted TCRs. In this study, we generated a novel platform cell line, CD4-2D3, in which GFP reporter was expressed by NFAT activation via TCR signaling, for correctly evaluating functional avidity of HLA class II-restricted TCRs. Furthermore, using this platform cell line, we succeeded in maturating functional avidity of an HLA class II-restricted TCR specific for a WT1-derived helper peptide by substituting amino acids in complementarity determining region 3 (CDR3) of the TCR. Importantly, we demonstrated that transduction of an avidity-maturated TCR conferred strong cytotoxicity against WT1-expressing leukemia cells on CD4+ T cells, compared to that of its original TCR. Thus, CD4-2D3 cell line should be useful not only to evaluate TCR functional avidity in HLA class II-restricted TCRs but also to screen appropriate TCRs for clinical applications such as cancer immunotherapy.

Smart Nanosystem-Mediated Inhibition of Mitochondrial Respiration for Enhanced Phototherapy-Induced Antitumor Immunity

Introduction

Here, based on oxygen-dependent photodynamic therapy (PDT) and oxygen-consumed oxidative phosphorylation of cancer tissues, we designed and developed a nanosystem (named CyI&Met-Liposome, LCM) to co-encapsulate the photosensitizer CyI and mitochondrial respiration inhibitor metformin (Met) as a PDT enhancer.

Methods

We synthesized nanoliposomes encapsulating Met and CyI with excellent photodynamic/photothermal and anti-tumor immune properties using a thin film dispersion method. Confocal microscopy and flow cytometry were used to assess the cellular uptake, PDT, photothermal therapy (PTT) and immunogenicity of nanosystem in vitro. Finally, two tumor models in mice were constructed to investigate the tumor suppression and immunity in vivo.

Results

The resulting nanosystem relieved hypoxia in tumor tissues, enhanced PDT efficiency, and amplified antitumor immunity induced by phototherapy. As a photosensitizer, CyI effectively killed the tumor by generating toxic singlet reactive oxygen species (ROS), while the addition of Met reduced oxygen consumption in tumor tissues, thereby evoking an immune response via oxygen-boosted PDT. Both in vitro and in vivo results illustrated that LCM effectively restricted the respiration of tumor cells to reduce tumor hypoxia, thus providing continuous oxygen for enhanced CyI-mediated PDT. Furthermore, T cells were recruited and activated at high levels, providing a promising platform to eliminate the primary tumors and synchronously realize effective inhibition of distant tumors.

T cells in health and disease

T cells are crucial for immune functions to maintain health and prevent disease. T cell development occurs in a stepwise process in the thymus and mainly generates CD4+ and CD8+ T cell subsets. Upon antigen stimulation, naïve T cells differentiate into CD4+ helper and CD8+ cytotoxic effector and memory cells, mediating direct killing, diverse immune regulatory function, and long-term protection. In response to acute and chronic infections and tumors, T cells adopt distinct differentiation trajectories and develop into a range of heterogeneous populations with various phenotype, differentiation potential, and functionality under precise and elaborate regulations of transcriptional and epigenetic programs. Abnormal T-cell immunity can initiate and promote the pathogenesis of autoimmune diseases. In this review, we summarize the current understanding of T cell development, CD4+ and CD8+ T cell classification, and differentiation in physiological settings. We further elaborate the heterogeneity, differentiation, functionality, and regulation network of CD4+ and CD8+ T cells in infectious disease, chronic infection and tumor, and autoimmune disease, highlighting the exhausted CD8+ T cell differentiation trajectory, CD4+ T cell helper function, T cell contributions to immunotherapy and autoimmune pathogenesis. We also discuss the development and function of γδ T cells in tissue surveillance, infection, and tumor immunity. Finally, we summarized current T-cell-based immunotherapies in both cancer and autoimmune diseases, with an emphasis on their clinical applications. A better understanding of T cell immunity provides insight into developing novel prophylactic and therapeutic strategies in human diseases.

p38MAPKα Stromal Reprogramming Sensitizes Metastatic Breast Cancer to Immunotherapy

Metastatic breast cancer is an intractable disease that responds poorly to immunotherapy. We show that p38MAPKα inhibition (p38i) limits tumor growth by reprogramming the metastatic tumor microenvironment in a CD4+ T cell-, IFNγ-, and macrophage-dependent manner. To identify targets that further increased p38i efficacy, we utilized a stromal labeling approach and single-cell RNA sequencing. Thus, we combined p38i and an OX40 agonist that synergistically reduced metastatic growth and increased overall survival. Intriguingly, patients with a p38i metastatic stromal signature had better overall survival that was further improved by the presence of an increased mutational load, leading us to ask if our approach would be effective in antigenic breast cancer. The combination of p38i, anti-OX40, and cytotoxic T-cell engagement cured mice of metastatic disease and produced long-term immunologic memory. Our findings demonstrate that a detailed understanding of the stromal compartment can be used to design effective antimetastatic therapies.

SIGNIFICANCE

Immunotherapy is rarely effective in breast cancer. We dissected the metastatic tumor stroma, which revealed a novel therapeutic approach that targets the stromal p38MAPK pathway and creates an opportunity to unleash an immunologic response. Our work underscores the importance of understanding the tumor stromal compartment in therapeutic design. This article is highlighted in the In This Issue feature, p. 1275.

Leveraging immune resistance archetypes in solid cancer to inform next-generation anticancer therapies

Anticancer immunotherapies, such as immune checkpoint inhibitors, bispecific antibodies, and chimeric antigen receptor T cells, have improved outcomes for patients with a variety of malignancies. However, most patients either do not initially respond or do not exhibit durable responses due to primary or adaptive/acquired immune resistance mechanisms of the tumor microenvironment. These suppressive programs are myriad, different between patients with ostensibly the same cancer type, and can harness multiple cell types to reinforce their stability. Consequently, the overall benefit of monotherapies remains limited. Cutting-edge technologies now allow for extensive tumor profiling, which can be used to define tumor cell intrinsic and extrinsic pathways of primary and/or acquired immune resistance, herein referred to as features or feature sets of immune resistance to current therapies. We propose that cancers can be characterized by immune resistance archetypes, comprised of five feature sets encompassing known immune resistance mechanisms. Archetypes of resistance may inform new therapeutic strategies that concurrently address multiple cell axes and/or suppressive mechanisms, and clinicians may consequently be able to prioritize targeted therapy combinations for individual patients to improve overall efficacy and outcomes.

In vivo CRISPR screens reveal Serpinb9 and Adam2 as regulators of immune therapy response in lung cancer

How the genetic landscape governs a tumor's response to immunotherapy remains poorly understood. To assess the immune-modulatory capabilities of 573 genes associated with altered cytotoxicity in human cancers, here we perform CRISPR/Cas9 screens directly in mouse lung cancer models. We recover the known immune evasion factors Stat1 and Serpinb9 and identify the cancer testis antigen Adam2 as an immune modulator, whose expression is induced by KrasG12D and further elevated by immunotherapy. Using loss- and gain-of-function experiments, we show that ADAM2 functions as an oncogene by restraining interferon and TNF cytokine signaling causing reduced presentation of tumor-associated antigens. ADAM2 also restricts expression of the immune checkpoint inhibitors PDL1, LAG3, TIGIT and TIM3 in the tumor microenvironment, which might explain why ex vivo expanded and adoptively transferred cytotoxic T-cells show enhanced cytotoxic efficacy in ADAM2 overexpressing tumors. Together, direct in vivo CRISPR/Cas9 screens can uncover genetic alterations that control responses to immunotherapies.

The multifaceted roles of CD4+ T cells and MHC class II in cancer surveillance

CD4⁺ T cells exhibit diverse functions in cancer surveillance. Concordantly, single-cell transcriptional analyses have revealed several distinct CD4⁺ T-cell differentiation states in tumours, including cytotoxic and regulatory subsets associated with favourable or unfavourable outcomes, respectively. These transcriptional states are determined and further shaped by dynamic interactions of CD4⁺ T cells with different types of immune cells, stromal cells and cancer cells. Therefore, we discuss the cellular networks in the tumour microenvironment (TME) that either promote or impede CD4⁺ T-cell cancer surveillance. We consider antigen/Major histocompatibility complexclass-II (MHC-II)-dependent interactions of CD4⁺ T cells with both professional antigen-presenting cells and cancer cells, the latter of which can directly express MHC-II, at least in some tumours. Additionally, we examine recent single-cell RNA sequencing studies that have shed light on the phenotype and functions of cancer-specific CD4⁺ T cells in human tumours.

Harnessing type I interferon-mediated immunity to target malignant brain tumors

Type I interferons have long been appreciated as a cytokine family that regulates antiviral immunity. Recently, their role in eliciting antitumor immune responses has gained increasing attention. Within the immunosuppressive tumor microenvironment (TME), interferons stimulate tumor-infiltrating lymphocytes to promote immune clearance and essentially reshape a "cold" TME into an immune-activating "hot" TME. In this review, we focus on gliomas, with an emphasis on malignant glioblastoma, as these brain tumors possess a highly invasive and heterogenous brain TME. We address how type I interferons regulate antitumor immune responses against malignant gliomas and reshape the overall immune landscape of the brain TME. Furthermore, we discuss how these findings can translate into future immunotherapies targeting brain tumors in general.

Tumor immune microenvironment (TIME) to enhance antitumor immunity

The tumor microenvironment is a result of dynamic interaction between different cellular and non-cellular components. In its essence it is not a solo performer, but an ensemble of performers that includes cancer cells, fibroblasts, myo-fibroblasts, endothelial cells and immune cells. The short review highlights important immune infiltrates within the tumor microenvironment that shape cytotoxic t lymphocyte (CTL)-rich immune hot and CTL-deficient immune cold tumors and novel strategies that have potential role in enhancing our immune responses in both immune hot and immune cold tumors.

Dual receptor T cells mediate effective antitumor immune responses via increased recognition of tumor antigens

BACKGROUND

Discovery that ~16% of T cells naturally co-express two T-cell receptor (TCR) clonotypes prompts examining the role of dual TCR cells in immune functions.

METHODS

Using TCRα-reporter transgenic mice, enabling unambiguous identification of single-TCR and dual-TCR cells, we tested the role of dual TCR cells in antitumor immune responses against immune-responsive syngeneic 6727 sarcoma and immune-resistant B16F10 melanoma.

RESULTS

Dual TCR cells were specifically increased among tumor-infiltrating lymphocytes (TILs) in both models, indicating selective advantage in antitumor responses. Phenotype and single-cell gene expression analyses identified dual TCR are predominant during the effective antitumor response, demonstrating selectively increased activation in the TIL compartment and skewing toward an effector memory phenotype. Absence of dual TCR cells impaired immune response to B16F10 but not 6727, suggesting that dual TCR cells may be more influential in responses against poorly immunogenic tumors. Dual TCR cells demonstrated an advantage in recognition of B16F10-derived neoantigens in vitro, providing a mechanistic basis for their antitumor reactivity.

CONCLUSIONS

These results discover an unrecognized role for dual TCR cells in protective immune function and identify these cells and their TCRs as a potential resource for antitumor immunotherapy.

Enhancing Efficacy of TCR-engineered CD4 + T Cells Via Coexpression of CD8α

Adoptive cell therapy with T cells expressing affinity-enhanced T-cell receptors (TCRs) is a promising treatment for solid tumors. Efforts are ongoing to further engineer these T cells to increase the depth and durability of clinical responses and broaden efficacy toward additional indications. In the present study, we investigated one such approach: T cells were transduced with a lentiviral vector to coexpress an affinity-enhanced HLA class I-restricted TCR directed against MAGE-A4 alongside a CD8α coreceptor. We hypothesized that this approach would enhance CD4 + T-cell helper and effector functions, possibly leading to a more potent antitumor response. Activation of transduced CD4 + T cells was measured by detecting CD40 ligand expression on the surface and cytokine and chemokine secretion from CD4 + T cells and dendritic cells cultured with melanoma-associated antigen A4 + tumor cells. In addition, T-cell cytotoxic activity against 3-dimensional tumor spheroids was measured. Our data demonstrated that CD4 + T cells coexpressing the TCR and CD8α coreceptor displayed enhanced responses, including CD40 ligand expression, interferon-gamma secretion, and cytotoxic activity, along with improved dendritic cell activation. Therefore, our study supports the addition of the CD8α coreceptor to HLA class I-restricted TCR-engineered T cells to enhance CD4 + T-cell functions, which may potentially improve the depth and durability of antitumor responses in patients.

Dynamics and specificities of T cells in cancer immunotherapy

Recent advances in cancer immunotherapy - ranging from immune-checkpoint blockade therapy to adoptive cellular therapy and vaccines - have revolutionized cancer treatment paradigms, yet the variability in clinical responses to these agents has motivated intense interest in understanding how the T cell landscape evolves with respect to response to immune intervention. Over the past decade, the advent of multidimensional single-cell technologies has provided the unprecedented ability to dissect the constellation of cell states of lymphocytes within a tumour microenvironment. In particular, the rapidly expanding capacity to definitively link intratumoural phenotypes with the antigen specificity of T cells provided by T cell receptors (TCRs) has now made it possible to focus on investigating the properties of T cells with tumour-specific reactivity. Moreover, the assessment of TCR clonality has enabled a molecular approach to track the trajectories, clonal dynamics and phenotypic changes of antitumour T cells over the course of immunotherapeutic intervention. Here, we review the current knowledge on the cellular states and antigen specificities of antitumour T cells and examine how fine characterization of T cell dynamics in patients has provided meaningful insights into the mechanisms underlying effective cancer immunotherapy. We highlight those T cell subsets associated with productive T cell responses and discuss how diverse immunotherapies might leverage the pre-existing tumour-reactive T cell pool or instruct de novo generation of antitumour specificities. Future studies aimed at elucidating the factors associated with the elicitation of productive antitumour T cell immunity are anticipated to instruct the design of more efficacious treatment strategies.

Human CD4 cytotoxic T lymphocytes mediate potent tumor control in humanized immune system mice

Efficacy of immune checkpoint inhibitors in cancers can be limited by CD8 T cell dysfunction or HLA-I down-regulation. Tumor control mechanisms independent of CD8/HLA-I axis would overcome these limitations. Here, we report potent CD4 T cell-mediated tumor regression and memory responses in humanized immune system (HIS) mice implanted with HT-29 colorectal tumors. The regressing tumors showed increased CD4 cytotoxic T lymphocyte (CTL) infiltration and enhanced tumor HLA-II expression compared to progressing tumors. The intratumoral CD4 T cell subset associated with tumor regression expressed multiple cytotoxic markers and exhibited clonal expansion. Notably, tumor control was abrogated by depletion of CD4 but not CD8 T cells. CD4 T cells derived from tumor-regressing mice exhibited HLA-II-dependent and tumor-specific killing ex vivo. Taken together, our study demonstrates a critical role of human CD4 CTLs in mediating tumor clearance independent of CD8 T cells and provides a platform to study human anti-tumor immunity in vivo.

Intratumor childhood vaccine-specific CD4+ T-cell recall coordinates antitumor CD8+ T cells and eosinophils

BACKGROUND

Antitumor mechanisms of CD4⁺ T cells remain crudely defined, and means to effectively harness CD4⁺ T-cell help for cancer immunotherapy are lacking. Pre-existing memory CD4⁺ T cells hold potential to be leveraged for this purpose. Moreover, the role of pre-existing immunity in virotherapy, particularly recombinant poliovirus immunotherapy where childhood polio vaccine specific immunity is ubiquitous, remains unclear. Here we tested the hypothesis that childhood vaccine-specific memory T cells mediate antitumor immunotherapy and contribute to the antitumor efficacy of polio virotherapy.

METHODS

The impact of polio immunization on polio virotherapy, and the antitumor effects of polio and tetanus recall were tested in syngeneic murine melanoma and breast cancer models. CD8⁺ T-cell and B-cell knockout, CD4⁺ T-cell depletion, CD4⁺ T-cell adoptive transfer, CD40L blockade, assessments of antitumor T-cell immunity, and eosinophil depletion defined antitumor mechanisms of recall antigens. Pan-cancer transcriptome data sets and polio virotherapy clinical trial correlates were used to assess the relevance of these findings in humans.

RESULTS

Prior vaccination against poliovirus substantially bolstered the antitumor efficacy of polio virotherapy in mice, and intratumor recall of poliovirus or tetanus immunity delayed tumor growth. Intratumor recall antigens augmented antitumor T-cell function, caused marked tumor infiltration of type 2 innate lymphoid cells and eosinophils, and decreased proportions of regulatory T cells (Tregs). Antitumor effects of recall antigens were mediated by CD4⁺ T cells, limited by B cells, independent of CD40L, and dependent on eosinophils and CD8⁺ T cells. An inverse relationship between eosinophil and Treg signatures was observed across The Cancer Genome Atlas (TCGA) cancer types, and eosinophil depletion prevented Treg reductions after polio recall. Pretreatment polio neutralizing antibody titers were higher in patients living longer, and eosinophil levels increased in the majority of patients, after polio virotherapy.

CONCLUSION

Pre-existing anti-polio immunity contributes to the antitumor efficacy of polio virotherapy. This work defines cancer immunotherapy potential of childhood vaccines, reveals their utility to engage CD4⁺ T-cell help for antitumor CD8⁺ T cells, and implicates eosinophils as antitumor effectors of CD4⁺ T cells.

H4-methylation regulators mediated epitranscriptome patterns and tumor microenvironment infiltration characterization in hepatocellular carcinoma

Epigenetic modifications are involved in the remodeling of the tumor microenvironment (TME) and the regulation of immune response. Nonetheless, the role of histone H4 methylation (H4M) modification in the TME and immune regulation of hepatocellular carcinoma (HCC) is unknown. As a result, the purpose of this research is to discover H4M-mediated modification patterns and their effects on TME and immunologic characteristics in HCC. A total of 2305 samples were enrolled from 13 different cohorts. With the help of consensus clustering analysis, three distinct H4M modification patterns were identified. The cell-infiltrating characteristics of TME under these three patterns were highly consistent with their enriched biological processes and clinical outcome. The H4Mscore was then created using principal component analysis algorithm to quantify the H4M modification pattern of each individual tumor and was systematically correlated with representative tumor characteristics. We found that analyzing H4M modification patterns within individual tumors could predict TME infiltration, homologous recombination deficiency (HRD), intratumor heterogeneity, proliferation activity, mRNA stemness index, and prognosis. The group with a low H4Mscore had an inflamed TME phenotype and a better immunotherapy response, as well as a better survival outcome. The prognostic value of H4Mscore was validated in three internal cohorts and five external cohorts, respectively. In external immunotherapy cohorts, the low H4Mscore was also linked to an enhanced response to anti-PD-1/L1 and anti-CTLA4 immunotherapy and a better prognosis. This study revealed that H4M modification played an important role in forming TME diversity and complexity. Evaluating the H4M modification pattern of individual tumors could help us learn more about TME and develop more effective immunotherapy strategies.

CD4+ T cells in cancer

Cancer immunology and immunotherapy are driving forces of research and development in oncology, mostly focusing on CD8⁺ T cells and the tumor microenvironment. Recent progress highlights the importance of CD4⁺ T cells, corresponding to the long-known fact that CD4⁺ T cells are central players and coordinators of innate and antigen-specific immune responses. Moreover, they have now been recognized as anti-tumor effector cells in their own right. Here we review the current status of CD4⁺ T cells in cancer, which hold great promise for improving knowledge and therapies in cancer.

In Situ Reprogramming of Tumor-Associated Macrophages with Internally and Externally Engineered Exosomes

The reprogramming of tumor-associated macrophages (TAMs) has emerged as an efficient strategy for immunotherapy. However, most of the approaches did not allow the in situ reprogramming of TAM because their low efficiency, non-specificity, or potential side effects. Herein, we produced exosomes with the clustered regularly interspaced short palindromic repeats interference (CRISPRi) internally engineered and the TAM specific peptide externally engineered onto the exosome membrane. The internally and externally engineered exosomes (IEEE, also named as I3E) allowed the selective homing to tumor tissue and targeted to M2-like TAMs, which nearly repressed the expression of PI-3 kinase gamma (PI3Kγ) completely, and induced the TAMs polarizing to M1 both in vitro and in vivo. The polarized M1 macrophages awakened the "hot" tumor-immunity, causing the increase of T lymphocyte infiltration and the decrease of myeloid-derived suppressor cells, and inhibiting the tumor growth significantly. I3E reprogramed TAMs in situ precisely and efficiently.

mTORC1 upregulates B7-H3/CD276 to inhibit antitumor T cells and drive tumor immune evasion

Identifying the mechanisms underlying the regulation of immune checkpoint molecules and the therapeutic impact of targeting them in cancer is critical. Here we show that high expression of the immune checkpoint B7-H3 (CD276) and high mTORC1 activity correlate with immunosuppressive phenotypes and worse clinical outcomes in 11,060 TCGA human tumors. We find that mTORC1 upregulates B7-H3 expression via direct phosphorylation of the transcription factor YY2 by p70 S6 kinase. Inhibition of B7-H3 suppresses mTORC1-hyperactive tumor growth via an immune-mediated mechanism involving increased T-cell activity and IFN-γ responses coupled with increased tumor cell expression of MHC-II. CITE-seq reveals strikingly increased cytotoxic CD38+CD39+CD4+ T cells in B7-H3-deficient tumors. In pan-human cancers, a high cytotoxic CD38+CD39+CD4+ T-cell gene signature correlates with better clinical prognosis. These results show that mTORC1-hyperactivity, present in many human tumors including tuberous sclerosis complex (TSC) and lymphangioleiomyomatosis (LAM), drives B7-H3 expression leading to suppression of cytotoxic CD4+ T cells.

Liujunzi decoction exerts potent antitumor activity in oesophageal squamous cell carcinoma by inhibiting miR-34a/STAT3/IL-6R feedback loop, and modifies antitumor immunity

BACKGROUND

Liujunzi decoction (LJZD), a traditional herbal formula and one of the most commonly used adjuvant medications for the treatment of oesophageal squamous cell carcinoma (ESCC), exerts good antitumor and immunomodulatory activity. However, its specific mechanism of action remains largely unclear.

PURPOSE

In order to examine the potential primary and adjuvant antitumor mechanisms of LJZD, both in vitro and in vivo.

METHODS

IL-6 and miR-34a inhibitors were used to activate the miR-34a/STAT3/IL-6R feedback loop to observe the effects of LJZD. A humanised mouse model with a functional human immune system was constructed to evaluate the antitumor efficacy of LJZD in vivo on xenograft tumours, which was compared to that of the positive control drug anti-PD-1 monoclonal antibodies (mAb). Finally, a co-culture system of peripheral blood mononuclear and tumour cells in vitro was used to analyse the cytotoxic activity of LJZD on T cells.

RESULTS

LJZD significantly interfered with IL-6-induced activation of the miR-34a/STAT3/IL-6R feedback loop in ESCC by restoring the expression of the tumour suppressor miR-34a, and inhibited the proliferation of EC109 oesophageal cancer cells in a dose-dependant manner. Furthermore, LJZD effectively suppressed oesophageal tumour growth in vivo and alleviated organ injury and visceral index. Furthermore, LJZD boosted antitumor immunity by increasing IFN-γ expression and CD8⁺tumour-infiltrating lymphocytes (TILs) infiltration in the peripheral blood and tumour tissues, respectively, which may be related to a decrease in PD-1, but not PD-L1 expression. Finally, we confirmed that LJZD strengthens the killing ability of T cells by suppressing PD-1 expression in a co-culture system in vitro.

CONCLUSION

LJZD exerts excellent antitumor effect by interfering with the miR-34a/STAT3/IL-6R feedback loop and augmenting antitumor immune responses. Which provides new insights into mechanisms for LJZD and sheds light on the multifaceted role of phytomedicine in cancer.

CD4+ cytotoxic T cells: an emerging effector arm of anti-tumor immunity

While CD8+ cytotoxic T cells have long been considered the primary effector in controlling tumors, the involvement of CD4+ "helper" T cells in anti-tumor immunity has been underappreciated. The investigations of intra-tumoral T cells, fueled by the recent advances in genomic technologies, have led to a rethinking of the indirect role of CD4+ T cells that have traditionally been described as a "helper". Accumulating evidence from preclinical and clinical studies indicates that CD4+ T cells can acquire intrinsic cytotoxic properties and directly kill various types of tumor cells in a major histocompatibility complex class II (MHC-II)-dependent manner, as opposed to the indirect "helper" function, thus underscoring a potentially critical contribution of CD4+ cytotoxic T cells to immune responses against a wide range of tumor types. Here, we discuss the biological properties of anti-tumor CD4+ T cells with cytotoxic capability and highlight the emerging observations suggesting their more significant role in anti-tumor immunity than previously appreciated. [BMB Reports 2023; 56(3): 140-144].

A novel inflammasome-related gene nomogram predicts survival in hepatocellular carcinoma

Inflammasomes are closely associated with the progression of multiple cancers. We established an inflammasome-related gene (IRG)-based model to predict the survival of patients with hepatocellular carcinoma (HCC). The RNA-sequencing data and clinical information of HCC patients were downloaded from the cancer genome atlas-liver hepatocellular carcinoma database, and the differentially expressed inflammasome-related gene were screened. Seven prognostic differentially expressed inflammasome-related genes were identified by univariate Cox analysis and incorporated into the risk model using least absolute shrinkage and selection operator-Cox algorithm. The predictive accuracy of the risk model was evaluated through the Kaplan-Meier, receiver operating characteristic and Cox regression analyses. The performance of the model was verified in the International Cancer Genome Consortium-Liver Cancer - RIKEN, JP cohort. A nomogram was constructed to predict the 1-, 2-, 3- ,and 5-year survival of HCC patients, and its performance was evaluated using calibration curves. The significantly enriched gene ontology terms, Kyoto encyclopedia of genes and genomes pathways and infiltrating immune cell populations associated with the IRG model were also analyzed to explore of the potential molecular mechanisms and immunotherapeutic targets. An independent and highly accurate prognostic model consisting of 7 IRGs was established and verified in 2 independent HCC cohorts. The IRG model was significantly associated with cell division and cell cycle. In addition, the high-risk group was more likely to have greater infiltration of immune cells and higher expression of immune checkpoint-related genes compared to the low-risk group. An IRG-based model was established to predict 1-, 2-, 3-, and 5-year survival rate in individual HCC patients, which provides new insights into the role of inflammasomes in HCC.

Learning from the nexus of autoimmunity and cancer

The immune system plays critical roles in both autoimmunity and cancer, diseases at opposite ends of the immune spectrum. Autoimmunity arises from loss of T cell tolerance against self, while in cancer, poor immunity against transformed self fails to control tumor growth. Blockade of pathways that preserve self-tolerance is being leveraged to unleash immunity against many tumors; however, widespread success is hindered by the autoimmune-like toxicities that arise in treated patients. Knowledge gained from the treatment of autoimmunity can be leveraged to treat these toxicities in patients. Further, the understanding of how T cell dysfunction arises in cancer can be leveraged to induce a similar state in autoreactive T cells. Here, we review what is known about the T cell response in autoimmunity and cancer and highlight ways in which we can learn from the nexus of these two diseases to improve the application, efficacy, and management of immunotherapies.

Tumor cells fail to present MHC-II-restricted epitopes derived from oncogenes to CD4+ T cells

CD4+ T cells play a critical role in antitumor immunity via recognition of peptide antigens presented on MHC class II (MHC-II). Although some solid cancers can be induced to express MHC-II, the extent to which this enables direct recognition by tumor-specific CD4+ T cells is unclear. We isolated and characterized T cell antigen receptors (TCRs) from naturally primed CD4+ T cells specific for 2 oncoproteins, HPV-16 E6 and the activating KRASG12V mutation, from patients with head and neck squamous cell carcinoma and pancreatic ductal adenocarcinoma, respectively, and determined their ability to recognize autologous or human leukocyte antigen-matched antigen-expressing tumor cells. We found in both cases that the TCRs were capable of recognizing peptide-loaded target cells expressing the relevant MHC-II or B cell antigen-presenting cells (APCs) when the antigens were endogenously expressed and directed to the endosomal pathway but failed to recognize tumor cells expressing the source protein even after induction of surface MHC-II expression by IFN-γ or transduction with CIITA. These results suggest that priming and functional recognition of both a nuclear (E6) and a membrane-associated (KRAS) oncoprotein are predominantly confined to crosspresenting APCs rather than via direct recognition of tumor cells induced to express MHC-II.

Bifunctional cancer cell-based vaccine concomitantly drives direct tumor killing and antitumor immunity

The administration of inactivated tumor cells is known to induce a potent antitumor immune response; however, the efficacy of such an approach is limited by its inability to kill tumor cells before inducing the immune responses. Unlike inactivated tumor cells, living tumor cells have the ability to track and target tumors. Here, we developed a bifunctional whole cancer cell-based therapeutic with direct tumor killing and immunostimulatory roles. We repurposed the tumor cells from interferon-β (IFN-β) sensitive to resistant using CRISPR-Cas9 by knocking out the IFN-β-specific receptor and subsequently engineered them to release immunomodulatory agents IFN-β and granulocyte-macrophage colony-stimulating factor. These engineered therapeutic tumor cells (ThTCs) eliminated established glioblastoma tumors in mice by inducing caspase-mediated cancer cell apoptosis, down-regulating cancer-associated fibroblast-expressed platelet-derived growth factor receptor β, and activating antitumor immune cell trafficking and antigen-specific T cell activation signaling. This mechanism-based efficacy of ThTCs translated into a survival benefit and long-term immunity in primary, recurrent, and metastatic cancer models in immunocompetent and humanized mice. The incorporation of a double kill-switch comprising herpes simplex virus-1 thymidine kinase and rapamycin-activated caspase 9 in ThTCs ensured the safety of our approach. Arming naturally neoantigen-rich tumor cells with bifunctional therapeutics represents a promising cell-based immunotherapy for solid tumors and establishes a road map toward clinical translation.

Prospective study of adoptive activated αβT lymphocyte immunotherapy for refractory cancers: development and validation of a response scoring system

BACKGROUND AIMS

This prospective clinical study aimed to determine the efficacy and prognostic factors of adoptive activated αβT lymphocyte immunotherapy for various refractory cancers. The primary endpoint was overall survival (OS), and the secondary endpoint was radiological response.

METHODS

The authors treated 96 patients. Activated αβT lymphocytes were infused every 2 weeks for a total of six times. Prognostic factors were identified by analyzing clinical and laboratory data obtained before therapy.

RESULTS

Median survival time (MST) was 150 days (95% confidence interval, 105-191), and approximately 20% of patients achieved disease control (complete response + partial response + stable disease). According to the multivariate Cox proportional hazards model with Akaike information criterion-best subset selection, sex, concurrent therapy, neutrophil/lymphocyte ratio, albumin, lactate dehydrogenase, CD4:CD8 ratio and T helper (Th)1:Th2 ratio were strong prognostic factors. Using parameter estimates of the Cox analysis, the authors developed a response scoring system. The authors then determined the threshold of the response score between responders and non-responders. This threshold was able to significantly differentiate OS of responders from that of non-responders. MST of responders was longer than that of non-responders (317.5 days versus 74 days). The validity of this response scoring system was then confirmed by internal validation.

CONCLUSIONS

Adoptive activated αβT lymphocyte immunotherapy has clinical efficacy in certain patients. The authors' scoring system is the first prognostic model reported for this therapy, and it is useful for selecting patients who might obtain a better prognosis through this modality.

Exhausted T cells hijacking the cancer-immunity cycle: Assets and liabilities

T cell exhaustion is an alternative differentiation path of T cells, sometimes described as a dysfunction. During the last decade, insights of T cell exhaustion acting as a bottle neck in the field of cancer immunotherapy have undoubtedly provoked attention. One of the main drivers of T cell exhaustion is prolonged antigen presentation, a prerequisite in the cancer-immunity cycle. The umbrella term "T cell exhaustion" comprises various stages of T cell functionalities, describing the dynamic, one-way exhaustion process. Together these qualities of T cells at the exhaustion continuum can enable tumor clearance, but if the exhaustion acquired timeframe is exceeded, tumor cells have increased possibilities of escaping immune system surveillance. This could be considered a tipping point where exhausted T cells switch from an asset to a liability. In this review, the contrary role of exhausted T cells is discussed.

Multiparametric flow cytometry to characterize vaccine-induced polyfunctional T cell responses and T cell/NK cell exhaustion and memory phenotypes in mouse immuno-oncology models

Suitable methods to assess in vivo immunogenicity and therapeutic efficacy of cancer vaccines in preclinical cancer models are critical to overcome current limitations of cancer vaccines and enhance the clinical applicability of this promising immunotherapeutic strategy. In particular, availability of methods allowing the characterization of T cell responses to endogenous tumor antigens is required to assess vaccine potency and improve the antigen formulation. Moreover, multiparametric assays to deeply characterize tumor-induced and therapy-induced immune modulation are relevant to design mechanism-based combination immunotherapies. Here we describe a versatile multiparametric flow cytometry method to assess the polyfunctionality of tumor antigen-specific CD4⁺ and CD8⁺ T cell responses based on their production of multiple cytokines after short-term ex vivo restimulation with relevant tumor epitopes of the most common mouse strains. We also report the development and application of two 21-color flow cytometry panels allowing a comprehensive characterization of T cell and natural killer cell exhaustion and memory phenotypes in mice with a particular focus on preclinical cancer models.

CD4+ T cell memory is impaired by species-specific cytotoxic differentiation, but not by TCF-1 loss

CD4⁺ T cells are typically considered as 'helper' or 'regulatory' populations that support and orchestrate the responses of other lymphocytes. However, they can also develop potent granzyme (Gzm)-mediated cytotoxic activity and CD4⁺ cytotoxic T cells (CTLs) have been amply documented both in humans and in mice, particularly in the context of human chronic infection and cancer. Despite the established description of CD4⁺ CTLs, as well as of the critical cytotoxic activity they exert against MHC class II-expressing targets, their developmental and memory maintenance requirements remain elusive. This is at least in part owing to the lack of a murine experimental system where CD4⁺ CTLs are stably induced. Here, we show that viral and bacterial vectors encoding the same epitope induce distinct CD4⁺ CTL responses in challenged mice, all of which are nevertheless transient in nature and lack recall properties. Consistent with prior reports, CD4⁺ CTL differentiation is accompanied by loss of TCF-1 expression, a transcription factor considered essential for memory T cell survival. Using genetic ablation of Tcf7, which encodes TCF-1, at the time of CD4⁺ T cell activation, we further show that, contrary to observations in CD8⁺ T cells, continued expression of TCF-1 is not required for CD4⁺ T cell memory survival. Whilst Tcf7-deficient CD4⁺ T cells persisted normally following retroviral infection, the CD4⁺ CTL subset still declined, precluding conclusive determination of the requirement for TCF-1 for murine CD4⁺ CTL survival. Using xenotransplantation of human CD4⁺ T cells into murine recipients, we demonstrate that human CD4⁺ CTLs develop and persist in the same experimental conditions where murine CD4⁺ CTLs fail to persist. These observations uncover a species-specific defect in murine CD4⁺ CTL persistence with implications for their use as a model system.

Biomarkers of tumor-reactive CD4+ and CD8+ TILs associate with improved prognosis in endometrial cancer

BACKGROUND

Despite the growing interest in immunotherapeutic interventions for endometrial cancer (EC), the prevalence, phenotype, specificity and prognostic value of tumor infiltrating lymphocytes (TILs) in this tumor type remains unclear.

METHODS

To better understand the role of TILs in EC, we analyzed the phenotypic traits of CD8⁺ and CD4⁺ EC^-resident T cells from 47 primary tumors by high-dimensional flow cytometry. In addition, CD8⁺ and CD4⁺ TIL subpopulations were isolated based on the differential expression of programmed cell death protein-1 (PD-1) (negative, dim and high) and CD39 (positive or negative) by fluorescence activated cell sorting (FACS), expanded in vitro, and screened for autologous tumor recognition. We further investigated whether phenotypic markers preferentially expressed on CD8⁺ and CD4⁺ tumor-reactive TIL subsets were associated with the four distinct molecular subtypes of EC, tumor mutational burden and patient survival.

RESULTS

We found that CD8⁺TILs expressing high levels of PD-1 (PD-1hi) co-expressed CD39, TIM-3, HLA-DR and CXCL13, as compared with TILs lacking or displaying intermediate levels of PD-1 expression (PD-1^- and PD-1^dim, respectively). Autologous tumor reactivity of sorted and in vitro expanded CD8+ TILs demonstrated that the CD8⁺PD-1^dimCD39⁺ and PD-1^hiCD39⁺ T cell subsets both contained tumor-reactive TILs and that a higher level of PD-1 expression was associated with increased CD39 and a superior frequency of tumor reactivity. With respect to CD4⁺ T conventional (Tconv) TILs, co-expression of inhibitory and activation markers was more apparent on PD-1^hi compared with PD-1^- or PD-1^dim T cells, and in fact, it was the CD4⁺PD-1^hi subpopulation that accumulated the antitumor T cells irrespective of CD39 expression. Most importantly, detection of CD8⁺PD-1^hiCD39+ and CD4⁺PD-1^hi tumor-reactive T-cell subsets, but also markers specifically expressed by these subpopulations of TILs, that is, PD-1^hi, CD39, CXCL13 and CD103 by CD8⁺ TILs and PD-1^hi and CXCL13 by CD4⁺ Tconv TILs, correlated with prolonged survival of patients with EC.

CONCLUSIONS

Our results demonstrate that EC are frequently infiltrated by tumor-reactive TILs, and that expression of PD-1^hi and CD39 or PD-1^hi can be used to select and expand CD8⁺ and CD4⁺ tumor-reactive TILs, respectively. In addition, biomarkers preferentially expressed on tumor-reactive TILs, rather than the frequency of CD3⁺, CD8⁺ and CD4⁺ lymphocytes, hold prognostic value suggesting their protective role in antitumor immunity.

Reduced Number and Immune Dysfunction of CD4+ T Cells in Obesity Accelerate Colorectal Cancer Progression

Obesity, a known risk factor for various types of cancer, reduces the number and function of cytotoxic immune cells in the tumor immune microenvironment (TIME). However, the impact of obesity on CD4+ T cells remains unclear. Therefore, this study aimed to clarify the impact of obesity on CD4+ T cells in the TIME. A tumor-bearing obese mouse model was established by feeding with 45% high-fat diet (HFD), followed by inoculation with a colon cancer cell line MC38. Tumor growth was significantly accelerated compared to that in mice fed a control diet. Tumor CD4+ T cells showed a significant reduction in number and an increased expression of programmed death-1 (PD-1), and decreased CD107a expression and cytokine such as IFN-γ and TNF-α production, indicating dysfunction. We further established CD4+ T cell-depleted HFD-fed model mice, which showed reduced tumor infiltration, increased PD-1 expression in CD8+ T cells, and obesity-induced acceleration of tumor growth in a CD4+ T cell-dependent manner. These findings suggest that the reduced number and dysfunction of CD4+ T cells due to obesity led to a decreased anti-tumor response of both CD4+ and CD8+ T cells to ultimately accelerate the progression of colorectal cancer. Our findings may elucidate the pathogenesis for poor outcomes of colorectal cancer associated with obesity.

Immunotherapy approaches for adult glioma: knowledge gained from recent clinical trials

PURPOSE OF REVIEW

Summarize principles behind various immunotherapy approaches for high and low-grade glioma in the context of recently completed clinical trials and the new insights they provide.

RECENT FINDINGS

Despite the widespread success of therapies targeting the T-cell checkpoints programmed-death 1 and cytotoxic T lymphocyte antigen 4 in other malignancies, recent phase III trials in glioblastoma confirm the lack of efficacy of anti-programmed-death 1 monotherapy in more than 90% of patients. Vaccination approaches remain under investigation for high-grade glioma and have shown activity in some low-grade glioma patients. Chimeric antigen receptor T cells now feature a new generation of products engineered to potentially withstand glucocorticoid therapy. Oncolytic viral therapies have similarly advanced in sophistication, with drug-sensitive gene expression and tumor-selective modifications. Combinations of therapies hold promise for overcoming the numerous mechanisms of immune suppression in glioma.

SUMMARY

Although immunotherapies have yet to show rates of efficacy compared with other malignancies, new knowledge of immunology and combination therapies brings hope for improved efficacy in the future.

T cell-mediated additive cytotoxicity - death by multiple bullets

Immune effector cells, including cytotoxic T cells (CTLs), induce apoptosis and eliminate target cells by direct cell-cell contacts. In vivo, CTLs fail to efficiently kill solid tumor cells by individual contacts but rely upon multihit interactions by many CTLs (swarming). Recent evidence has indicated that multihit interactions by CTLs induce a series of sublethal damage events in target cells, including perforin-mediated membrane damage, induction of reactive oxygen species (ROS), nuclear envelope rupture, and DNA damage. Individual damage can be repaired, but when induced in rapid sequence, sublethal damage can accumulate and induce target cell death. Here, we summarize the sublethal damage and additive cytotoxicity concepts for CTL-induced and other cell stresses and discuss the implications for improving immunotherapy and multitargeted anticancer therapies.

Regulation of CD4 T Cell Responses by the Transcription Factor Eomesodermin

Central to the impacts of CD4 T cells, both positive in settings of infectious disease and cancer and negative in the settings of autoimmunity and allergy, is their ability to differentiate into distinct effector subsets with specialized functions. The programming required to support such responses is largely dictated by lineage-specifying transcription factors, often called ‘master regulators’. However, it is increasingly clear that many aspects of CD4 T cell immunobiology that can determine the outcomes of disease states involve a broader transcriptional network. Eomesodermin (Eomes) is emerging as an important member of this class of transcription factors. While best studied in CD8 T cells and NK cells, an increasing body of work has focused on impacts of Eomes expression in CD4 T cell responses in an array of different settings. Here, we focus on the varied impacts reported in these studies that, together, indicate the potential of targeting Eomes expression in CD4 T cells as a strategy to improve a variety of clinical outcomes.

Delineating the transcriptional landscape and clonal diversity of virus-specific CD4+ T cells during chronic viral infection

Although recent evidence indicates that CD4+ T cells responding to chronic viral infection are functionally heterogenous, our understanding of the developmental relationships between these subsets, and a determination of how their transcriptional landscape compares to their acute infection counterparts remains unclear. Additionally, whether cell-intrinsic factors such as TCR usage influence CD4+ T cell fate commitment during persistent infection has not previously been studied. Herein, we perform single-cell RNA sequencing (scRNA-seq) combined with single-cell T cell receptor sequencing (scTCR-seq) on virus-specific CD4+ T cells isolated from mice infected with chronic lymphocytic choriomeningitis virus (LCMV) infection. We identify several transcriptionally distinct states among the Th1, Tfh, and memory-like T cell subsets that form at the peak of infection, including the presence of a previously unrecognized Slamf7+ subset with cytolytic features. We further show that the relative distribution of these populations differs substantially between acute and persistent LCMV infection. Moreover, while the progeny of most T cell clones displays membership within each of these transcriptionally unique populations, overall supporting a one cell-multiple fate model, a small fraction of clones display a biased cell fate decision, suggesting that TCR usage may impact CD4+ T cell development during chronic infection. Importantly, comparative analyses further reveal both subset-specific and core gene expression programs that are differentially regulated between CD4+ T cells responding to acute and chronic LCMV infection. Together, these data may serve as a useful framework and allow for a detailed interrogation into the clonal distribution and transcriptional circuits underlying CD4+ T cell differentiation during chronic viral infection.

Nanoparticle-based modulation of CD4+ T cell effector and helper functions enhances adoptive immunotherapy

Helper (CD4+) T cells perform direct therapeutic functions and augment responses of cells such as cytotoxic (CD8+) T cells against a wide variety of diseases and pathogens. Nevertheless, inefficient synthetic technologies for expansion of antigen-specific CD4+ T cells hinders consistency and scalability of CD4+ T cell-based therapies, and complicates mechanistic studies. Here we describe a nanoparticle platform for ex vivo CD4+ T cell culture that mimics antigen presenting cells (APC) through display of major histocompatibility class II (MHC II) molecules. When combined with soluble co-stimulation signals, MHC II artificial APCs (aAPCs) expand cognate murine CD4+ T cells, including rare endogenous subsets, to induce potent effector functions in vitro and in vivo. Moreover, MHC II aAPCs provide help signals that enhance antitumor function of aAPC-activated CD8+ T cells in a mouse tumor model. Lastly, human leukocyte antigen class II-based aAPCs expand rare subsets of functional, antigen-specific human CD4+ T cells. Overall, MHC II aAPCs provide a promising approach for harnessing targeted CD4+ T cell responses.

Facts and Hopes in the Relationship of EBV with Cancer Immunity and Immunotherapy

Epstein-Barr virus (EBV), the first identified human tumor virus, infects and takes up residency in almost every human. However, EBV genome-positive tumors arise in only a tiny minority of infected people, presumably when the virus-carrying tumor cells are able to evade immune surveillance. Traditional views regard viral antigens as the principal targets of host immune surveillance against virus-infected cells. However, recent findings indicate that EBV-infected/-transformed B cells elicit both cytotoxic CD8+ and CD4+ T-cell responses against a wide range of overexpressed cellular antigens known to function as tumor-associated antigens (TAA), in addition to various EBV-encoded antigens. This not only broadens the ways by which the immune system controls EBV infection and prevents it from causing cancers, but also potentially extends immune protection toward EBV-unrelated cancers by targeting shared TAAs. The goal of this review is to incorporate these new findings with literature data and discuss future directions for improved understanding of EBV-induced antitumor immunity, as well as the hopes for rational immune strategies for cancer prevention and therapy.

Cancer cell autophagy, reprogrammed macrophages, and remodeled vasculature in glioblastoma triggers tumor immunity

Glioblastoma (GBM) is poorly responsive to therapy and invariably lethal. One conceivable strategy to circumvent this intractability is to co-target distinctive mechanistic components of the disease, aiming to concomitantly disrupt multiple capabilities required for tumor progression and therapeutic resistance. We assessed this concept by combining vascular endothelial growth factor (VEGF) pathway inhibitors that remodel the tumor vasculature with the tricyclic antidepressant imipramine, which enhances autophagy in GBM cancer cells and unexpectedly reprograms immunosuppressive tumor-associated macrophages via inhibition of histamine receptor signaling to become immunostimulatory. While neither drug is efficacious as monotherapy, the combination of imipramine with VEGF pathway inhibitors orchestrates the infiltration and activation of CD8 and CD4 T cells, producing significant therapeutic benefit in several GBM mouse models. Inclusion up front of immune-checkpoint blockade with anti-programmed death-ligand 1 (PD-L1) in eventually relapsing tumors markedly extends survival benefit. The results illustrate the potential of mechanism-guided therapeutic co-targeting of disparate biological vulnerabilities in the tumor microenvironment.

Multiplexed In Situ Spatial Protein Profiling in the Pursuit of Precision Immuno-Oncology for Patients with Breast Cancer

Immune checkpoint inhibitors (ICIs) have revolutionized the treatment of many solid tumors. In breast cancer (BC), immunotherapy is currently approved in combination with chemotherapy, albeit only in triple-negative breast cancer. Unfortunately, most patients only derive limited benefit from ICIs, progressing either upfront or after an initial response. Therapeutics must engage with a heterogeneous network of complex stromal-cancer interactions that can fail at imposing cancer immune control in multiple domains, such as in the genomic, epigenomic, transcriptomic, proteomic, and metabolomic domains. To overcome these types of heterogeneous resistance phenotypes, several combinatorial strategies are underway. Still, they can be predicted to be effective only in the subgroups of patients in which those specific resistance mechanisms are effectively in place. As single biomarker predictive performances are necessarily suboptimal at capturing the complexity of this articulate network, precision immune-oncology calls for multi-omics tumor microenvironment profiling in order to identify unique predictive patterns and to proactively tailor combinatorial treatments. Multiplexed single-cell spatially resolved tissue analysis, through precise epitope colocalization, allows one to infer cellular functional states in view of their spatial organization. In this review, we discuss-through the lens of the cancer-immunity cycle-selected, established, and emerging markers that may be evaluated in multiplexed spatial protein panels to help identify prognostic and predictive patterns in BC.

CD4 + Cytotoxic T Lymphocytes in Cancer Immunity and Immunotherapy

CD4⁺ T cells have the ability to differentiate into relatively specialized effector subsets after exposure to innate immune signals. The remarkable plasticity of CD4⁺ T cells is required to achieve immune responses in different tissues and against various pathogens. Numerous studies have shown that CD4⁺ T cells can play direct and indispensable roles in protective immunity by killing infected or transformed cells. Although the lineage decision of commitment to the CD4⁺ or CD8⁺ cell lineage is once thought to be inflexible, the identification of antigen-experienced CD4⁺ T cells with cytotoxic activity suggests the existence of unexpected plasticity for these cells. The recognition of CD4⁺ cytotoxic T lymphocytes (CTLs) and the mechanisms driving the differentiation of this particular cell subset create opportunities to explore the roles of these effector cells in protective immunity and immune-related pathology. CD4⁺ CTLs are proven to play a protective role in antiviral immunity. Here, the latest investigations on the phenotypic and functional features of CD4⁺ CTLs and their roles in antitumor immunity and immunotherapy are briefly reviewed.

The PD-1/PD-L1 Pathway: A Perspective on Comparative Immuno-Oncology

Simple Summary

The programmed cell death protein 1/programmed death-ligand 1 (PD-1/PD-L1) pathway inhibits the function of activated immune cells. This mediates immune tolerance and prevents immune-mediated tissue destruction. The malfunction of this pathway is involved in the pathogenesis of chronic infections, autoimmunity, and cancer. The PD-1/PD-L1 pathway is an excellent example of the research benefits of comparative pathology and attests to the importance of the “one health one medicine” concept. Pioneering research was mainly focused on the examination of cells and tissues of human and mouse origin. It mainly revealed that PD-L1-positive tumor cells can paralyze PD-1-bearing immune cells, which prevents immunological destruction of cancer cells. This led to a major breakthrough in cancer treatment, i.e., the use of antibodies that block the interaction of these molecules and restore anti-cancer immune defense (immune checkpoint therapy). Further studies provided more detailed information on the tissue-specific context and fine-tuning of this pathway. The most recent research has extended the investigations to the examination of several animal species with the aim of improving disease diagnostics and treatment for certain animal diseases, in particular cancer, which is a major cause of disease and death in companion animals.

Abstract

The programmed cell death protein 1/programmed death-ligand 1 (PD-1/PD-L1) pathway mainly attracted attention in immuno-oncology, leading to the development of immune checkpoint therapy. It has, however, much broader importance for tissue physiology and pathology. It mediates basic processes of immune tolerance and tissue homeostasis. In addition, it is involved in the pathogenesis of chronic infectious diseases, autoimmunity, and cancer. It is also an important paradigm for comparative pathology as well as the “one health one medicine” concept. The aim of this review is to provide an overview of novel research into the diverse facets of the PD-1/PD-L1 pathway and to give insights into its fine-tuning homeostatic role in a tissue-specific context. This review details early translational research from the discovery phase based on mice as animal models for understanding pathophysiological aspects in human tissues to more recent research extending the investigations to several animal species. The latter has the twofold goal of comparing this pathway between humans and different animal species and translating diagnostic tools and treatment options established for the use in human beings to animals and vice versa.

Engineered red blood cells (activating antigen carriers) drive potent T cell responses and tumor regression in mice

Activation of T cell responses is essential for effective tumor clearance; however, inducing targeted, potent antigen presentation to stimulate T cell responses remains challenging. We generated Activating Antigen Carriers (AACs) by engineering red blood cells (RBCs) to encapsulate relevant tumor antigens and the adjuvant polyinosinic-polycytidylic acid (poly I:C), for use as a tumor-specific cancer vaccine. The processing method and conditions used to create the AACs promote phosphatidylserine exposure on RBCs and thus harness the natural process of aged RBC clearance to enable targeting of the AACs to endogenous professional antigen presenting cells (APCs) without the use of chemicals or viral vectors. AAC uptake, antigen processing, and presentation by APCs drive antigen-specific activation of T cells, both in mouse in vivo and human in vitro systems, promoting polyfunctionality of CD8+ T cells and, in a tumor model, driving high levels of antigen-specific CD8+ T cell infiltration and tumor killing. The efficacy of AAC therapy was further enhanced by combination with the chemotherapeutic agent Cisplatin. In summary, these findings support AACs as a potential vector-free immunotherapy strategy to enable potent antigen presentation and T cell stimulation by endogenous APCs with broad therapeutic potential.

Comprehensive analysis of FRAS1/FREM family as potential biomarkers and therapeutic targets in renal clear cell carcinoma

Background: FRAS1 (Fraser syndrome protein 1), together with FREM1 (the Fras1-related extracellular matrix proteins 1) and FREM2, belonging to the FRAS1/FREM extracellular matrix protein family, are considered to play essential roles in renal organogenesis and cancer progression. However, their roles in kidney renal clear cell carcinoma (KIRC) remain to be elucidated. Methods: FRAS1/FREM RNA expression analysis was performed using TCGA/GTEx databases, and valided using GEO databases and real-time PCR. Protein expression was peformed using CPTAC databases. Herein, we employed an array of bioinformatics methods and online databases to explore the potential oncogenic roles of FRAS1/FREM in KIRC. Results: We found that FRAS1, FREM1 and FREM2 genes and proteins expression levels were significantly decreased in KIRC tissues than in normal tissues. Decreased FRAS1/FREM expression levels were significantly associated with advanced clinicopathological parameters (pathological stage, grade and tumor metastasis status). Notably, the patients with decreased FRAS1/FREM2 expression showed a high propensity for metastasis and poor prognosis. FRAS1/FREM were correlated with various immune infiltrating cells, especially CD4+ T cells and its corresponding subsets (Th1, Th2, Tfh and Tregs). FRAS1 and FREM2 had association with DNA methylation and their single CpG methylation levels were associated with prognosis. Moreover, FRAS1/FREM might exert antitumor effects by functioning in key oncogenic signalling pathways and metabolic pathways. Drug sensitivity analysis indicated that high FRAS1 and FREM2 expression can be a reliable predictor of targeted therapeutic drug response, highlighting the potential as anticancer drug targets. Conclusion: Together, our results indicated that FRAS1/FREM family members could be potential therapeutic targets and valuable prognostic biomarkers of KIRC.

Comprehensive analysis about prognostic and immunological role of WTAP in pan-cancer

Background: Wilms tumor 1-associated protein (WTAP) plays a critical role in ribonucleic acid (RNA) methylation of N6 adenosine (m6A) modification, which is closely related with varieties of biological process. However, the role of WTAP in cancers remains to be determined. This study is designed to demonstrate the prognostic landscape of WTAP in pan-cancer and explore the relationship between WTAP expression and immune infiltration. Methods: Here, we investigated the expression level and prognostic role of WTAP in pan-cancer using multiple databases, including PrognoScan, GEPIA, and Kaplan-Meier Plotter. Then, applying the GEPIA and TIMER databases, we illustrated the correlations between WTAP expression and immune infiltration in tumors, especially liver hepatocellular carcinoma (LIHC), and esophageal carcinoma (ESCA). Results: WTAP had significant higher expression levels in tumor tissues of ESCA, LIHC, etc., while lower expression levels in those of bladder urothelial carcinoma (BLCA), breast invasive carcinoma (BRCA), etc. And WTAP demonstrated multifaceted prognostic value in cancers. Of our interests, WTAP exerted a harmful effect on LIHC patient for overall survival (OS) and progression free survival (PFS). WTAP expression also significantly associated with the infiltration levels of B cells, CD8+ T cells, CD4+ T cells, macrophages, neutrophils, and dendritic cells (DC) in LIHC but not ESCA. Furthermore, combined analysis about WTAP expression level and immune cell specific gene markers implied WTAP correlates with regulatory cells (T reg) infiltration in LIHC and ESCA. Conclusion: The m6A regulator WTAP can serve as a prognostic biomarker for certain tumor types in pan-cancer and potentially result from immune cell infiltration.

Distinct gene expression by expanded clones of quiescent memory CD4+ T cells harboring intact latent HIV-1 proviruses

Antiretroviral therapy controls, but does not cure, HIV-1 infection due to a reservoir of rare CD4+ T cells harboring latent proviruses. Little is known about the transcriptional program of latent cells. Here, we report a strategy to enrich clones of latent cells carrying intact, replication-competent HIV-1 proviruses from blood based on their expression of unique T cell receptors. Latent cell enrichment enabled single-cell transcriptomic analysis of 1,050 CD4+ T cells belonging to expanded clones harboring intact HIV-1 proviruses from 6 different individuals. The analysis reveals that most of these cells are T effector memory cells that are enriched for expression of HLA-DR, HLA-DP, CD74, CCL5, granzymes A and K, cystatin F, LYAR, and DUSP2. We conclude that expanded clones of latent cells carrying intact HIV-1 proviruses persist preferentially in a distinct CD4+ T cell population, opening possibilities for eradication.

Effective generation of tumor-infiltrating lymphocyte products from metastatic non-small-cell lung cancer (NSCLC) lesions irrespective of location and previous treatments

Background

Non-small-cell lung cancer (NSCLC) is the leading cause of cancer-related mortality worldwide. Because current treatment regimens show limited success rates, alternative therapeutic approaches are needed. We recently showed that treatment-naïve, stage I/II primary NSCLC tumors contain a high percentage of tumor-reactive T cells, and that these tumor-reactive T cells can be effectively expanded and used for the generation of autologous tumor-infiltrating T cell (TIL) therapy. Whether these promising findings also hold true for metastatic lesions is unknown yet critical for translation into the clinic.

Materials and methods

We studied the lymphocyte composition using flow cytometry from 27 metastatic NSCLC lesions obtained from different locations and from patients with different histories of treatment regimens. We determined the expansion capacity of TILs with the clinically approved protocol, and measured their capacity to produce the key pro-inflammatory cytokines interferon-γ, tumor necrosis factor and interleukin 2 and to express CD137 upon co-culture of expanded TILs with the autologous tumor digest.

Results

The overall number and composition of lymphocyte infiltrates from the various metastatic lesions was by and large comparable to that of early-stage primary NSCLC tumors. We effectively expanded TILs from all metastatic NSCLC lesions to numbers that were compatible with TIL transfusion, irrespective of the location of the metastasis and of the previous treatment. Importantly, 16 of 21 (76%) tested TIL products displayed antitumoral activity, and several contained polyfunctional T cells.

Conclusions

Metastatic NSCLC lesions constitute a viable source for the generation of tumor-reactive TIL products for therapeutic purposes irrespective of their location and the pre-treatment regimens.

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T cells can be efficiently isolated and expanded from late-stage NSCLC lesions.

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TIL products from metastatic NSCLC lesions are polyfunctional.

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Metastatic location or pre-treatment regimen does not affect T cells.

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Adoptive TIL therapy is a therapeutic option for late-stage NSCLC patients.

Transcriptional and functional analyses of neoantigen-specific CD4 T cells during a profound response to anti-PD-L1 in metastatic Merkel cell carcinoma

BACKGROUND

Merkel cell carcinoma (MCC) often responds to PD-1 pathway blockade, regardless of tumor-viral status (~80% of cases driven by the Merkel cell polyomavirus (MCPyV)). Prior studies have characterized tumor-specific T cell responses to MCPyV, which have typically been CD8, but little is known about the T cell response to UV-induced neoantigens.

METHODS

A patient in her mid-50s with virus-negative (VN) MCC developed large liver metastases after a brief initial response to chemotherapy. She received anti-PD-L1 (avelumab) and had a partial response within 4 weeks. Whole exome sequencing (WES) was performed to determine potential neoantigen peptides. Characterization of peripheral blood neoantigen T cell responses was evaluated via interferon-gamma (IFNγ) ELISpot, flow cytometry and single-cell RNA sequencing. Tumor-resident T cells were characterized by multiplexed immunohistochemistry.

RESULTS

WES identified 1027 tumor-specific somatic mutations, similar to the published average of 1121 for VN-MCCs. Peptide prediction with a binding cut-off of ≤100 nM resulted in 77 peptides that were synthesized for T cell assays. Although peptides were predicted based on class I HLAs, we identified circulating CD4 T cells targeting 5 of 77 neoantigens. In contrast, no neoantigen-specific CD8 T cell responses were detected. Neoantigen-specific CD4 T cells were undetectable in blood before anti-PD-L1 therapy but became readily detectible shortly after starting therapy. T cells produced robust IFNγ when stimulated by neoantigen (mutant) peptides but not by the normal (wild-type) peptides. Single cell RNAseq showed neoantigen-reactive T cells expressed the Th1-associated transcription factor (T-bet) and associated cytokines. These CD4 T cells did not significantly exhibit cytotoxicity or non-Th1 markers. Within the pretreatment tumor, resident CD4 T cells were also Th1-skewed and expressed T-bet.

CONCLUSIONS

We identified and characterized tumor-specific Th1-skewed CD4 T cells targeting multiple neoantigens in a patient who experienced a profound and durable partial response to anti-PD-L1 therapy. To our knowledge, this is the first report of neoantigen-specific T cell responses in MCC. Although CD4 and CD8 T cells recognizing viral tumor antigens are often detectible in virus-positive MCC, only CD4 T cells recognizing neoantigens were detected in this patient. These findings suggest that CD4 T cells can play an important role in the response to anti-PD-(L)1 therapy.

Paving the Way to Solid Tumors: Challenges and Strategies for Adoptively Transferred Transgenic T Cells in the Tumor Microenvironment

T cells are important players in the antitumor immune response. Over the past few years, the adoptive transfer of genetically modified, autologous T cells-specifically redirected toward the tumor by expressing either a T cell receptor (TCR) or a chimeric antigen receptor (CAR)-has been adopted for use in the clinic. At the moment, the therapeutic application of CD19- and, increasingly, BCMA-targeting-engineered CAR-T cells have been approved and have yielded partly impressive results in hematologic malignancies. However, employing transgenic T cells for the treatment of solid tumors remains more troublesome, and numerous hurdles within the highly immunosuppressive tumor microenvironment (TME) need to be overcome to achieve tumor control. In this review, we focused on the challenges that these therapies must face on three different levels: infiltrating the tumor, exerting efficient antitumor activity, and overcoming T cell exhaustion and dysfunction. We aimed to discuss different options to pave the way for potent transgenic T cell-mediated tumor rejection by engineering either the TME or the transgenic T cell itself, which responds to the environment.

Concomitant Cytotoxic Effector Differentiation of CD4+ and CD8+ T Cells in Response to EBV-Infected B Cells

Simple Summary

The Epstein–Barr virus (EBV) is a γ-herpes virus that primarily infects human B cells, and more than 90% of adults have experienced infection. EBV⁺ B cells express several viral proteins, transmitting signals important for the transformation and tumorigenesis of the infected B cells. Immune surveillance by the host immune system is important to suppress such abnormal expansion of EBV-infected B cells. Here we found that both CD4⁺ T cells and CD8⁺ T cells show similar gene expression patterns relating to cytotoxicity towards EBV-infected B cells. EBV-specific cytotoxic CD4⁺ T cells markedly expressed T-bet, Granzyme B, and Perforin alongside killing activity, which could reflect mechanisms shared with cytotoxic CD8⁺ T cells. Our findings support the concept that, upon EBV and perhaps other viral infections, T cells of different subsets can be drawn into common pathways mediating immune surveillance through cytotoxicity.

Abstract

Most people infected by EBV acquire specific immunity, which then controls latent infection throughout their life. Immune surveillance of EBV-infected cells by cytotoxic CD4⁺ T cells has been recognized; however, the molecular mechanism of generating cytotoxic effector T cells of the CD4⁺ subset remains poorly understood. Here we compared phenotypic features and the transcriptome of EBV-specific effector-memory CD4⁺ T cells and CD8⁺ T cells in mice and found that both T cell types show cytotoxicity and, to our surprise, widely similar gene expression patterns relating to cytotoxicity. Similar to cytotoxic CD8⁺ T cells, EBV-specific cytotoxic CD4⁺ T cells from human peripheral blood expressed T-bet, Granzyme B, and Perforin and upregulated the degranulation marker, CD107a, immediately after restimulation. Furthermore, T-bet expression in cytotoxic CD4⁺ T cells was highly correlated with Granzyme B and Perforin expression at the protein level. Thus, differentiation of EBV-specific cytotoxic CD4⁺ T cells is possibly controlled by mechanisms shared by cytotoxic CD8⁺ T cells. T-bet-mediated transcriptional regulation may explain the similarity of cytotoxic effector differentiation between CD4⁺ T cells and CD8⁺ T cells, implicating that this differentiation pathway may be directed by environmental input rather than T cell subset.

CRISPR screening identifies T cell-intrinsic regulators of CD3-bispecific antibody responses

CD3-engaging bispecific antibodies (BsAbs) enable the formation of an immune synapse between T cells and tumor cells, resulting in robust target cell killing not dependent on a preexisting tumor specific T cell receptor. While recent studies have shed light on tumor cell-specific factors that modulate BsAb sensitivity, the T cell-intrinsic determinants of BsAb efficacy and response durability are poorly understood. To better clarify the genes that shape BsAb-induced T cell responses, we conducted targeted analyses and a large-scale unbiased in vitro CRISPR/Cas9-based screen to identify negative regulators of BsAb-induced T cell proliferation. These analyses revealed that CD8+ T cells are dependent on CD4+ T cell-derived signaling factors in order to achieve sustained killing in vitro. Moreover, the mammalian target of rapamycin (mTOR) pathway and several other candidate genes were identified as intrinsic regulators of BsAb-induced T cell proliferation and/or activation, highlighting promising approaches to enhancing the utility of these potent therapeutics.